Red bait zone on the Romelia

Sea life: Sea squirts

Small sea squirts at Long Beach
Small sea squirts at Long Beach

Sea squirts are unromantic creatures, but close examination of their charms may be rewarded. They are also called ascidians. They have highly complex bodies, though you’d never say so just based on an external examination! They belong to the same phylum as humans – Chordata – because they have a primitive backbone.

Large red bait in the Atlantic
Large red bait in the Atlantic

Ascidians are either solitary (independent creatures) or colonial, where a group of individual elements called zooids forms an interdependent colony. Here’s  a picture of a colonial ascidian taken at Long Beach. Note the siphons all over the surface. Each member of the colony has a pair, but the nutrients they take in benefit the entire colony.

Colonial ascidians at Long Beach
Colonial ascidians at Long Beach

These creatures are a beautiful example of harmonious co-operation, and often form beautiful patterns.

Colonial ascidians at Long Beach
Colonial ascidians at Long Beach

And here are some solitary ascidians:

Sea squirts at Long Beach
Sea squirts at Long Beach

Their bodies are shaped like sacs, with an inlet and an outlet siphons called the oral and atrial siphons respectively. They take in water through their mouths, filter out the nutrients, and eject the water through the atrial siphon. They’re often shaped just like hearts (real ones, not the kind you draw for your Valentine).

Sea squirt at Long Beach
Sea squirt at Long Beach

Ascidians don’t have eyes, but they can sense light, and they can smell things. If you touch one it’ll close off its siphons.

Heart shaped sea squirt at Long Beach
Heart shaped sea squirt at Long Beach

They have a tough outer coating or tunic, hence the name of the subphylum they belong to, Tunicata (tunicates). Red bait, so called because it is used by fishermen, is common along the South African coast. If you were to cut open the leathery outer casing of any of the solitary ascidians in the images shown, you’d find a pink to red blobby interior which is what the fishermen chop up for bait.

Sea squirts at Partridge Point
Sea squirts at Partridge Point

Sea squirts often form the base on which a lot of other sea life grows. The picture above was taken at Partridge Point, and you can just see the siphons sticking out among all the other ocean goodness.

Red bait zone near the MV Romelia
Red bait zone near the MV Romelia

The red bait zone on the Atlantic side of the Cape Peninsula near Llandudno (and all along that coast) is beautiful, in rusty browns and reds interspersed with purple. We did our safety stop at that depth (less than 8 metres) when we dived the MV Romelia in December 2010, and spent the time admiring the beautiful sea squirts on the pinnacles around us.

Red bait zone on the Romelia
Red bait zone on the Romelia

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Clare

Lapsed mathematician, creator of order, formulator of hypotheses. Lover of the ocean, being outdoors, the bush, reading, photography, travelling (especially in Africa) and road trips.

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